In their letter - entitled: Have we forgotten how to bring up our children? - lead signatory Sue Palmer, author of Toxic Childhood and a former head teacher, claims the government has failed to understand how children develop.

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The national curriculum and a psychologically abusive education system have to be called to account

The group also includes former Children's Laureate Michael Morpurgo, child care expert, Dr Penelope Leach and environmentalist Sir Jonathan Porritt.

They warn that poor diet, restricting exercise, putting children in "academic straitjackets", and dressing them like "mini adults" will "restrict their creativity and enrichment".

The end of their letter reads: "Our society rightly takes great pains to protect children from physical harm, but seems to have lost sight of their emotional and social needs.

"However, it's now clear that the mental health of an unacceptable number of children is being unnecessarily compromised, and that this is almost certainly a key factor in the rise of substance abuse, violence and self-harm amongst our young people."

The childhood experienced by today's children is significantly different from that of previous generations